1. Field of the Invention
This invention relates to automotive evaporative emissions canisters. Such structures of this type employ a carbon-filled foam which adds adsorptive performance to the canister without having to enlarge the canister or having to change the carbon in the canister to a higher performance carbon.
2. Description of the Related Art
Presently, in the automotive industry, there are concerns with canister designs because these canisters either sometimes pass or fail enhanced evaporative emissions tests. Changing of the canister design is usually considered expensive; therefore, other solutions that incorporate a standard design are sought.
One remedy is to use a higher activity carbon. Typically, this results in a 15-20% gain in gasoline working capacity (GWC). However, if the initial design specifies the higher activity carbon, only small gains in GWC can be achieved by substituting a carbon with a slightly higher butane working capacity (BWC). Also, the changing of the minimum BWC of the carbon will add only a small amount of GWC to the canister.
It is also known to employ porous filter materials to restrain the carbon and collect the dust. Exemplary of such prior art are U.S. Pat. No. 4,598,686 ('686) to P. J. Lupoli et al., entitled "Fuel Vapor Recovery System For Automotive Vehicles," U.S. Pat. No. 4,683,862 ('862) to J. Fornuto et al., entitled "Fuel Vapor Storage Canister," U.S. Pat. No. 4,853,009 ('009) to K. W. Turner et al., entitled "Multi Orientation Fuel Vapor Storage Canister Assembly," and U.S. Pat. No. 5,098,453 ('453) to K. W. Turner et al., entitled "Vapor Storage Canister With Volume Change Compensator." While the '686, '862, '009, and '453 references teach automotive evaporative emissions canisters, they employ the use of various types of "filters" which take up valuable space, but do not improve the GWC. Consequently, a more advantageous canister, then, would be presented if the foam could be reduced or modified.
Finally, it is known to employ a "formed block" of carbon in an automotive evaporative emissions canister. Exemplary of such prior art is U.S. Pat. No. 5,453,118 ('118) to R. B. Heiligman, entitled "Carbon-Filled Fuel Vapor Filter System." While the 118 reference employs the use of a formed block of pellets or granules of carbon, this whole bed of carbon must be glued together to form this rigid formed block. Consequently, a further advantageous canister, then, would be presented if this expensive forming step could be eliminated.
It is apparent from the above that there exists a need in the art for an automotive evaporative emissions canister which is lightweight through simplicity of parts and uniqueness of structure, and which at least equals the adsorptive characteristics of the known canisters, but which at the same time has an increased gasoline working capacity (GWC). It is the purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.